Transistors are a bulwark of electronic switching and memory applications due to their extreme reliability and high ON/OFF ratios of 104-105. Transistors are three-terminal devices that include source, drain, and gate electrode terminals. Corresponding two-terminal electronic devices, having only a source and a drain, typically have ON/OFF ratios that are orders of magnitude smaller than transistors. Two-terminal electronic devices can be operable in switching and memory applications, if the devices display a non-linear current-versus-voltage response and have a great enough and reliable ON/OFF ratio.
Molecular-based devices and one-dimensional carbon nanostructures having non-linear current-versus-voltage response and current peak-to-valley ratios (PVRs) generally on the order of 2 to 100 have been reported. Likewise, two-terminal memory devices have been described that are based upon metal filamentary mechanisms. These include molecular-spaced devices, nanowire crossbar memories, and resistive random access memories using transition metal oxides. Two-terminal electronic devices, which contain conductive carbon sheets deposited between two electrode terminals and which display a non-linear current-versus-voltage response, have been described in co-pending and commonly owned U.S. patent application Ser. No. 12/240,673 and PCT application PCT/US08/78152. The two-terminal electronic devices reported therein display high ON/OFF ratios and can be written and read multiple times in memory applications.
Feasible fabrication of two-terminal electronic devices into arrays having a high device density is favorable for many electronics applications. High-density array fabrication techniques may encompass a three-dimensional orientation of the electronic devices in the array. A three-dimensional, two-terminal memory device array has been reported based on a conventional P-N junction. The nature of the P-N junction disclosed provides a device array capable of only being written a single time, however.
In view of the foregoing, development of two-terminal electronic devices exhibiting nonlinear current-versus-voltage response, having high and reliable ON/OFF ratios characterized by large current PVRs, and having the capability to be fabricated in high-density device arrays is of substantial benefit. Such electronic devices and arrays may have applications in electronic switching, memory, and sensor applications. Particularly in memory applications, devices and arrays having stable, re-writable, non-volatile, and non-destructive read memories with fast switching times are of substantial benefit in countless electronics applications where computer memory is used.